Mortar adapted for firing from a light vehicle

ABSTRACT

A mortar comprising a gun barrel mounted on a hinged support and provided with an elastic device to accommodate recoil and return the barrel to initial position after firing. The elastic device is constructed as an assembly of overlapping annular elastic elements which surround the gun barrel and are carried in a cradle mounted on the support. The annular elements undergo sliding on one another during recoil at which time the elements undergo radial deformation, and subsequently the annular elements elastically return to their original configuration to restore the gun barrel to its initial position. Various ways are disclosed to limit the stress applied to the endmost annular elements to make the stress distribution in the annular elements more uniform along the length of the assembly. The mortar is rear loaded through a radially movable loading head which in the firing position is in rearward prolongation of the gun barrel.

United States Patent [1 1 Marest et al.

l MORTAR ADAPTED FOR FIRING FROM A LIGHT VEHICLE I 75] Inventors: MichelPaul Marest, Paris; Rene Paul Fraymann, Clamart, both of France; PierreMarie Biarrote, deceased, late of Clamart, France, by Christiane AndreeGermaine Dubois, administrator [73] Assignee: Etat F rancais, Paris,France [22] Filed: Dec. 6, 1972 [2|] Appl. No.: 312,497

[30] Foreign Application Priority Data Dec. 7, 1971 France 7l.43875 [52]US. Cl. 89/37 C; 89/44 R [51] Int. Cl F4" 19/06 [58] Field of Search89/] G, I F, l J, 37 C, 89/37 A. 37 B, 37, 44

f 56] References Cited UNITED STATES PATENTS 2,370,835 3/1945 Beu et al89/49 R 2,484,053 l0/l949 Rosenkrantz r 89/! .l X 2,962,935 l2/l960Hepperle 89/44 R 3,l8l,82l 5/l965 Eddins 183/! C X 3,50l.997 3/!970Winsen et al. 89/37 C [451 July 15, 1975 FOREIGN PATENTS OR APPLICATIONS5] 1.165 5/]952 Belgium 89/44 R 7l7,()50 2/l942 Germany... v. 89/44 R[57] ABSTRACT A mortar comprising a gun barrel mounted on a hingedsupport and provided with an elastic device to accommodate recoil andreturn the barrel to initial position after firing. The elastic deviceis constructed as an assembly of overlapping annular elastic elementswhich surround the gun barrel and are carried in a cradle mounted on thesupport. The annular elements undergo sliding on one another duringrecoil at which time the elements undergo radial deformation, andsubsequently the annular elements elastically return to their originalconfiguration to restore the gun barrel to its initial position, Variousways are disclosed to limit the stress applied to the endmost annularelements to make the stress distribution in the annular elements moreuniform along the length of the assembly. The mortar is rear loadedthrough a radially movable loading head which in the firing position isin rearward prolongation of the gun barrel.

6 Claims, 13 Drawing Figures MORTAR ADAPTED FOR FIRING FROM A LIGHTVEHICLE FIELD OF THE INVENTION The invention relates to mortars, andparticularly to medium-caliber high-angle fire ordnance manned byinfantry units.

PRIOR ART The light-mortar ordnance in current use is transported inseparate parts (gun tube, bedplate, bipod) by being carried and it mustbe assembled each time to be ready for firing. The parts are carriedwith difficulty and slowly, which is particularly inconvenient inasmuchas after they have fired a small number of rounds, mortars are easilypinpointed, by radar for example, and the gunners are not protected. Itis therefore extremely desirable that such ordnance be carried, mannedand fired on light transport vehicles.

Furthermore, mortars of the aforesaid type are muzzle loaded, whichinvolves a certain number of disadvantages. Firstly the risks ofaccidents are fairly large because of the chances of double loading.Also, the length of the gun tube is restricted, which precludesincreasing the performance of such ordnance. It is therefore anadvantage if these mortars can be breech loaded.

SUMMARY OF THE INVENTION An object of the present invention is toprovide a mortar which meets the aforesaid conditions.

The mortar of the invention is particularly noteworthy in that itcomprises an elastic connector or buffer device composed essentially ofa spring collar which absorbs the kinetic energy of recoil by elasticityand friction.

It is known that spring collars, composed of annular spring elementshaving taper faces and sliding over each other have the characteristicof restoring only a small proportion of the kinetic energy they haveabsorbed, the restored kinetic energy being used to obtain the return tofiring position. Due to such a buffer device, the stress of the gunmounting during each firing is greatly reduced and it then becomespossible to fire from a light armored vehicle.

According to one embodiment of the invention, the buffer devicecomprises a spring collar arranged concentrically around the gun tubeand surrounded by a cradle which is provided at both of its ends with aninside stop, and two rotary pistons, namely a recoil piston and a returnpiston floatably mounted on the gun tube on both sides of the springcollar and abutting against a respective inside stop of the cradle.

Such a floating assembly allows the recoiling mass to act compressivelyin both directions on the spring collar.

The annular members of the spring collar are subject to great impactforces which produce extremely high stresses in very short periods oftime. The maximum stress is of the order of several metric tons persquare centimeter and this is reached in a few thousandths of a secondwhen firing. This time interval is very substantially less than thestress propagation constant along the annular spring collar, whichconstant is dependent on the inertia of the spring members or rings andtheir frictional strength. It therefore follows that the end ringsundergo very great strain whereas the middle rings are subjected to asubstantially lesser strain. The distribution of these strains andconsequently the deformation of the rings is therefore not uniform allalong the length of the annular spring collar. The end rings subjectedto the greatest stresses tend to become fatigued and wear away quickly,consequently altering the spring characteristics.

A further object of the invention is to provide an embodiment of anannular spring collar in which the stresses are distributed as evenly aspossible whereby the life of the annular spring collar is increased.

According to the invention, the flexure capacity, i.e. the capability ofradial deformation of the end rings of the annular spring collar isrestricted to a value less than the equivalent of the maximumdeformation of the ring.

Preferably, to obtain uniform distribution of stresses the capacity forflexure of the rings is increased gradu ally from one end toward thecentral portion of the spring collar, the flexure capacity beinggreatest in the central portion.

According to a particular embodiment of the invention, the flexurecapacity is restricted by means of a hoop mounted around an inside ringof the spring collar between two outer rings. This hoop can, forexample, be made of piano wire.

In one variant of the invention, the sectional area of the rings in thecentral portion of the spring collar is less than that of the end rings.

In another variant, the width of the rings in the central portion of thespring collar is less than that of the end rings.

In still another variant, the frictional resistance of the rings of thecentral portion of the spring collar is less than the frictionalresistance of the end rings.

In still another variant, the angles ofinclination of the slidingsurfaces of the rings are different for the end rings and those at thecentral portion.

Another characteristic feature of the invention is the provision ofaguide forthe annular spring collar constituted as one or severalintermediate rings.

According to another characteristic feature of the invention, the mortarcomprises one or more movable loading heads perpendicularly displaceablerelative to the gun tube axis in a rear extension of the gun tube.

According to another embodiment of the invention, the mortar comprises abreech, the movable portion of which carries a loading head and moves ina mortise attached to a foot of the gun tube.

BRIEF DESCRIPTION OF THE DRAWING The invention will be describedhereunder in detail with reference to the attached drawings, wherein:

FIG. 1 is a sectional view ofa mortar according to the invention,showing the buffer device;

FIG. 2 is a sectional view of the mortar as seen in FIG. 1, illustratingthe loading device in detail;

FIG. 3 is a transverse view of the mortar of FIG. 1, looking toward theloading head;

FIG. 4 illustrates diagrammatically the mortar according to theinvention in a turret mounting;

FIG. 5 is a sectional view of the charging head;

FIGS. 6-a, 6-b and 6-c respectively illustrate the moving portion of theblock breech in a front view; a side elevation view and a sectional viewtaken on line 6c-6c in FIG. 6b;

FIG. '7 is a section illustrating the attachment of the loading head;

FIG. 8 is a graph diagrammatically explaining the operation of thespring collar;

FIG. 9 shows the characteristic curve of a spring collar;

FIG. 10 illustrates a partial section of a spring collar according tothe invention; and

FIG. 11 illustrates a spring collar provided with intermediate guiderings.

DETAILED DESCRIPTION The mortar illustrated in FIG. 1 essentiallycomprises a gun tube 1 and a loading and firing device which will bedescribed later. In accordance with the invention, the mortar isequipped with a buffer device composed essentially of a spring collar 11which at each time of firing absorbs the kinetic energy and restoresonly a small portion thereof to the gun tube mounting. The spring collar11 is arranged concentrically on gun tube 1. Arranged respectively atboth ends of the spring collar 11 are a recoil piston 12 and a returnpiston 13 floatably mounted on gun tube 1. A cradle 8 surrounds theassembly of the spring collar and pistons 12 and 13 and the pistonsimpinge internally in cradle 8 when the mortar is at rest.Advantageously, a protective shield 9 is attached to the cradle 8. Theassembly of cradle 8 and shield 9 is fastened by means of trunnions 18(FIG. 3) to the mortar mounting, which for example can be a lightarmored vehicle. The trunnions 18 allow the inclination of the mortar tobe changed. Air holes 14 machined in cradle 8 allow cooling of thespring collar 11.

The spring collar is essentially composed of annular members or rings101, 102 which are slidable on one another and which upon firing of theweapon are sub jected to axial force produced by recoil of the barrel 1.The axial force is applied to the spring collar via pistons 12 and 13and the rings slide on one another and resist recoil while storingenergy due to radial deformation of the rings so that at the end ofstroke, the rings return to their original diameter and in the course ofsliding on one another return the gun barrel 1 to its initial position.The construction of the spring collar will be described in greaterdetail later with reference to the assembly by which the application ofexcess stress to the endmost rings is avoided.

FIG. 8 shows the operation of the spring collar of the buffer device andthe applied force is plotted on the ordinate and the deformation of thespring collar along the abscissa. The first working stage is shown at 1this being the phase at the time of recoil, the shaded portioncorresponding to the recoil energy, the spring collar then acting as aresistance to recoil. Phase II corresponds to the return, the springcollar then acting as a recuperator and the corresponding shaded zonerepresenting spring expansion energy. During the other two phases IIIand IV, the spring collar acts as a return buffer, the correspondingshaded areas respectively representing the return energy and the springrelaxation energy.

FIG. 9 illustrates the characteristic curve of a ring of the springcollar wherein the stresses exerted are plotted on the ordinate and theelongation of the spring on the abscissa. The top curve corresponds tothe stressed phase of the spring and the bottom curve to its relaxationphase. If the spring is under strain at the maximum admissible loadduring its use, its life is drastically limited. On the other hand, ifit is subjected to stresses not exceeding percent of its maximumpermissible stress, 10,000 cycles can be imposed before the spring willbecome fatigued, that is to say until its characteristics alter. That iswhy, according to the invention, the force applied to the end rings ofthe spring collar which are the first to undergo strain, is limited. Theoperation of the spring can, for example, be precluded in zone A asindicated below, while providing operation in zone B with zone C forminga safety zone.

In one arrangement in which the stresses to which the end rings aresubjected is limited, hoops are mounted on the inside rings of thespring between the outer rings. This is illustrated in FIG. 10 where oneend of the spring collar is shown in section.

Therein it can be seen the annular spring collar is composed of insiderings 101 and outside rings 102. The spring collar comprises at one endone-half of an inside ring 103 acting as a supporting ring. The insideand outside rings are staggered, each outside ring contacting two insiderings and vice versa. Contact is made along symmetrical annular slidingsurfaces 104 and 104 which are inclined in section relative to thecenterline of the spring.

According to the invention, the deformation of the end rings is limitedby means of hoops 105 mounted around rings 101 between two outside rings102. The thickness of hoop 105 defines the maximum deformation of therings; as a matter of fact, when the spring collar is subjected tostress, the outside rings impinge on hoop 105 and the stress istransmitted directly to the succeeding inner rings. Thus the deformationof the end rings is limited by distributing the strain borne by thespring collar over all of the rings starting from the end where thestrain is exerted to the other end. Stated in another way, the hoops 105prevent the outer rings from undergoing radial expansion beyond aparticular limit thereby restricting the stress to which the outer ringswill be subjected.

The hoops 105 must be made of a substance offering sufficient strengthto resist the compression imposed by the outside rings 102 when theyabut the hoops. By way of example, hoops of 1.5 mm diameter piano wireare applicable for a spring collar of a diameter of 14 cm. Such a springcollar is shown in FlG. 11 and the spring collar comprises 50 elements,each element corresponding to one outside half-ring and one insidehalfring as shown at 108 in FIG. 10. To avoid deflection of the springcollar because of its length, intermediate guide rings 106 are uniformlyspaced along the interior of the collar. The rings 106 are internalrings provided with an annular flange 107 completely filling the spacebetween two corresponding outside rings.

The spring collar is advantageously provided with the hoops 105throughout its length and all elements are similar. This in fact allowsspring re-assembly operations to be simiplified, for example. afteroverhaul. This is important, since the maintenance operations must becapable under difficult conditions and by unskilled personnel.

If the stresses are to be more evenly distributed along the springcollar, the deformations of the rings can be limited to variouspre-determined values, the value of maximum deformation increasing fromthe end rings toward the middle rings. This can be obtained. forinstance, by the use of hoops whose thickness decreases from the endstoward the middle portion of the spring collar. Because the springcollar operates in both directions, it is advantageous for it to be ofsymmetrical design.

The desired distribution of stresses can also be obtained by acting onthe stress propagation constant in the spring collar. Thus, in onevariant of the invention, the cross-sectional area of the rings, i.e.their inertia, is made to vary, the central rings having the smallestsectional area. Likewise the width of the rings can be decreased, thenarrowest rings being in the middle portion.

To change the inertia of the rings, their frictional resistance can alsobe modified especially by altering the angles of inclination of thesliding surfaces.

The invention allows production of annular spring collars whose lengthof life corresponds with that of the other components of the mortar sothat the annular spring collar does not have to be changed. Furthermore,because of the better distribution of stresses, the spring collar can besubjected to greater stresses and thereby heavier charges can be usedfor the mortar.

The mortar is charged or loaded by means of one or more movable loadingheads which are displaceable perpendicularly to the gun tube axis so asto extend into an extension at the rear of the gun tube.

In the embodiment specifically illustrated in FIGS. 5-7, the mortarcomprises a single loading head 4 which is rigidly connected with themovable portion 3 of a breech whose carrier block 2 is attached to therear end of gun tube 1 and comprises a mortise in which the portion 3 isslidably mounted. The loading head extends in prolongation of the guntube when the breech is in closed position. The head 4 is made of gunsteel and accordingly proportioned. The portion 3 is illustrated indetail in FIGS. 6-0, 6-b and 6-4:.

The loading of the mortar according to the invention is effected byplacing a projectile in the loading head 4 when the breech is open (theposition shown in FIG. 2), then the breech is closed by moving theportion 3 to the position shown in FIG. 1.

The projectile percussion is controlled shot by shot, for example,automatically when the breech reaches its closed position. The firingmechanism is shown dia grammatically at 7. To facilitate loading, a feedaperture 10 is formed along the gun tube in extension of the head 4 whenthe portion 3 is in open position. In this way, as can be seen from FIG.2, the loading is effected in a particularly simple manner, since allthat is needed is to insert the projectile 6 into aperture 10, afterwhich the projectile then drops automatically into head 4 by gravity. Adevice can be provided for locking the breech in its open position, anda pushrod controlled by the gunner can release the breech so that it canautomatically arrive at a closed position.

It is of advantage for the length of the loading head to be sufficientso that the top end of projectile 6, when inside the head, may belocated at a very small distance from the front edge of the loadinghead. This serves as a protection against faulty entry of projectile 6inside the loading head, since in such case, the end of the projectilewill project beyond the loading head and hinder the closing of thebreech. To adapt the mortar to various types of projectiles, all that isnecessary is to provide easy replacement of the loading head for thetype of missile used. A larger movement of head 4 toward the top ofportion 3 can be provided, so as to free the loading head 4 completelyfrom the foot of gun tube 1 and bring it out of portion 3 through thetop. A single loading head can also be provided whose dimensions areequivalent to the longest projectile likely to be used in the mortar.

When closed, the loading head 4 makes contact at its front flange with agas obturator 5 arranged at the rear portion of gun tube 1, suchobturator being of known type to allow good tightness to be obtainedduring the firing.

As shown in FIG. 4, the mortar according to the invention, can easily beplaced in a turret l6 rotatable on a runway 17. Such turret can belocated on a light vehicle, which allows the mortar and its gun crew tobe moved quickly keeping them under shelter at the same time. Accordingto one variant, the mortar may be provided with a plurality of chargingheads arranged so as to form a barrel, each head successively enteringthe portion 3 as an extension of the gun tube.

The mortar according to the invention offers a number of advantages.First of all, as already mentioned above, because of the presence of thespring collar buffer, it can be carried and fired on a light vehicle onwhich it is mounted. it is, therefore, extremely mobile and can bereadied for firing in an extremely short time. Moreover, the gun crewcan be protected by armor plating carried by the vehicle. The safety ofthe crew is much improved because there is no muzzle loading but ratherbreech loading, the mortar being manned wholly inside the protectivearmor.

Furthermore, there is no restriction as to weight or of gun tube lengthas the mortar can be carried on a vehicle and loaded through the rear.Mortars can therefore be contemplated using projectiles offering betterperformance than those currently known, especially in regard to range.

It is to be noted that the manning of the weapon remains identical inevery respect as that of conventional mortars in current use, sinceloading and closing of the breech are effected by gravity.

The mortar according to the invention offers a high degree of safetysince it is loaded from the rear and the percussion is controlled.Moreover, there no longer is any risk of accident due to a doubleloading.

By the use of a turret, a bearing angle of 360 degrees can be obtained.

What is claimed is:

l. A mortar comprising a gun barrel having front and rear ends, supportmeans for said gun barrel, and elastic means connecting the gun barreland the support means and permitting recoil of the barrel upon firingwhile absorbing energy to return the barrel to initial position afterfiring, said elastic means including an assembly of annular eleasticelements surrounding the gun barrel, said annular elements beingarranged as alternating overlapped inner and outer rings having inclinedsurfaces in slidable arrangement on one another, said outer rings havingspaces between adjacent rings to enable the outer rings to slide on theinner rings and undergo radial expansion, and means for limiting radialexpansion of adjacent outer rings at the ends of the assembly to limitthe maximum stress applied to such rings and thereby distribute thestresses to the outer rings over the entire length of the assembly, thelatter said means comprising hoops surrounding the inner ringssubstantially centrally thereof and freely mounted in the spaces betweensaid adjacent outer rings, and spaced therefrom, said hoops having apre-determined thickness defining the maximum deformation for said outerrings and thereby limiting the maximum stress to which the outer ringsare subjected at the ends of the assembly.

2. A mortar as claimed in claim 1 wherein the elastic means furthercomprises a pair of spaced pistons loosely mounted on the gun barrel,said annular elements extending between said pistons and a cradleattached to said support means and carrying said pistons and annularelements.

3. A mortar as claimed in claim 2 wherein said elastic means is soconstructed that deformation capability of the annular rings increasesprogressively from the ends of the assembly to the middle portionthereof, the deformation capability being greatest in said middleportion, the cross-sectional area of the rings at the middle portions ofthe assembly being less than that of the rings at the ends of theassembly.

4. A mortar as claimed in claim 3 wherein the width of the rings at themiddle portion of the assembly being less than that of the rings at theends of the assembly.

5. A mortar as claimed in claim 2 wherein said elastic means is soconstructed that the deformation capability of the annular ringsincreases progressively from the ends of the assembly to the middleportion thereof, the deformation capability being greatest in saidmiddle portion, the sliding surfaces of the rings in the middle portionof the assembly having frictional resistance which is less than that ofthe rings at the ends of the assembly.

6. A mortar as claimed in claim 2 wherein said elastic means is soconstructed that the deformation capability of the annular ringsincreases progressively from the ends of the assembly to the middleportion thereof, the deformation capability being greatest in saidmiddle portion, the sliding surfaces of the annular rings havingdifferent angles of inclination for the rings in the middle portion andfor the rings at the ends of the assembly.

1. A mortar comprising a gun barrel having front and rear ends, supportmeans for said gun barrel, and elastic means connecting the gun barreland the support means and permitting recoil of the barrel upon firingwhile absorbing energy to return the barrel to initial position afterfiring, said elastic means including an assembly of annular eleasticelements surrounding the gun barrel, said annular elements beingarranged as alternating overlapped inner and outer rings having inclinedsurfaces in slidable arrangement on one another, said outer rings havingspaces between adjacent rings to enable the outer rings to slide on theinner rings and undergo radial expansion, and means for limiting radialexpansion of adjacent outer rings at the ends of the assembly to limitthe maximum stress applied to such rings and thereby distribute thestresses to the outer rings over the entire length of the assembly, thelatter said means comprising hoops surrounding the inner ringssubstantially centrally thereof and freely mounted in the spaces betweensaid adjacent outer rings, and spaced therefrom, said hoops having apre-determined thickness defining the maximum deformation for said outerrings and thereby limiting the maximum stress to which the outer ringsare subjected at the ends of the assembly.
 2. A mortar as claimed inclaim 1 wherein the elastic means further comprises a pair of spacedpistons loosely mounted on the gun barrel, said annular elementsextending between said pistons and a cradle attached to said supportmeans and carrying said pistons and annular elements.
 3. A mortar asclaimed in claim 2 wherein said elastic means is so constructed thatdeformation capability of the annular rings increases progressively fromthe ends of the assembly to the middle portion thereof, the deformationcapability being greatest in said middle portion, the cross-sectionalarea of the rings at the middle portions of the assembly being less thanthat of the rings at the ends of the assembly.
 4. A mortar as claimed inclaim 3 wherein the width of the rings at the middle portion of theassembly being less than that of the rings at the ends of the assembly.5. A mortar as claimed in claim 2 wherein said elastic means is soconstructed that the deformation capability of the annular ringsincreases progressively from the ends of the assembly to the middleportion thereof, the deformation capability being greatest in saidmiddle portion, the sliding surfaces of the rings in the middle portionof the assembly having frictional resistance which is less than that ofthe rings at the ends of the assembly.
 6. A mortar as claimed in claim 2wherein said elastic means is so constructed that the deformationcapability of the annular rings increases progressively from the ends ofthe assembly to the middle portion thereof, the deformation capabilitybeing greatest in said middle portion, the sliding surfaces of theannular rings having different angles of inclination for the rings inthe middle portion and for the rings at the ends of the assembly.